Without limiting the scope of the invention, its background is described in connection with the degradation of AZO dyes and organic pollutants. AZO dyes, generated from industrial waste, create an alarming threat as toxic water pollutant and carcinogen. A very recent study reported that AZO dyes decrease the permeability of blood-brain barrier, which may result in chronic neurological disorder in the human body. Transition metals (Fe, Ni) and noble metals (Pt, Pd) have been used to degrade and detoxify different organic water pollutants, including AZO dye. Noble metals typically show high catalytic activity. However, high cost, scarcity, and susceptibility to catalyst poisoning limit their application as water purifier. Thus, late transition metals like Fe, Ni, and Fe—Ni bi-metallic catalyst are attractive owing to their low cost, excellent catalytic performance, and easy availability in different forms. However, poor durability and high reactivity in aqueous medium restrict their potential use as a water purifier. In addition, these metals in elemental form exhibit wide range of toxicity in human body including cancer formation.
U.S. Pat. No. 9,149,673, entitled, “Removal of organic dyes and organic pollutants by titanium peroxide gel,” discloses a one step process of removal of chromophore/dye/organic pollutant from a solution comprising a polymer free titanium oxide gel i.e. high zeta potential is disclosed. The concentration of the chromophores is removed up to 95-100%.
China Patent Application No. 1415565, entitled, “Method for treating waste water of azo dye,” discloses a process for treating the sewage containing azo dye includes such steps as regulating pH value to less than 2.5, adding iron powder, stirring for decoloring, and radiating by ultraviolet light for optical degradation. Its advantages are high speed and effect, and no secondary pollution.
China Patent Application No. 104174380, entitled, “Green environment-friendly degradable adsorption material for azo dye industrial wastewater,” discloses a green environment-friendly degradable adsorption material for azo dye industrial wastewater is characterized by comprising the following substances in parts by weight: 10-32 parts of acrylic high-molecular water-absorption material, 3-9 parts of phosphoric acid, 5-14 parts of concentrated hydrochloric acid, 14-26 parts of ethanol, 5-16 parts of ammonia water, 3-6 parts of gallic acid, 2-6 parts of citric acid, 1-6 parts of diatomite, 3-8 parts of perforated expanded perlite, and 4-11 parts of a phosphite anti-oxidant. The beneficial effects comprise that the green environment-friendly degradable adsorption material is high in adsorption property, is capable of adsorbing azo dye molecules in azo dye wastewater into a tiny network to reach the effect of efficiently absorbing azo dye molecules in wastewater, and is good in processing effect; and also dye wastes subjected to adsorption can be used as a pigment of plastic and building materials.
China Patent Application No. 103585998, entitled, “Material for treating azo dye industrial wastewater,” discloses a material for treating azo dye industrial wastewater, which is characterized by comprising the following components in parts by weight: 10-32 parts of acrylic acid high-polymer water-absorbing resin, 10-25 parts of bagasse, 1-2 parts of nano calcium sulfate, 2-7 parts of titanate coupling agent, 0.1-0.3 part of nano silver, 1-2 parts of maleic anhydride graft polypropylene, 2-3 parts of polyethylene terephthalate, 10-16 parts of cement ash water solution, 9-15 parts of ferric oxide, 1-3 parts of high-density polyethylene (HDPE), 3-4 parts of toughener EOC and 1-3 parts of stearic acid. The material has high absorptivity, can adsorb azo dye molecules in azo dye wastewater into small networks, achieves the effect of efficiently absorbing azo dye molecules in wastewater, and has favorable treatment effect. The dye waste after adsorption can be used as a pigment for plastics and building materials.